Rotational Slip – glacial ice moving in a circular motion. It can help to make hollows in the landscape, deepening them into bowl shapes

She was rotating on slippers (rotational slip) made of ice. No wonder she moved so fast in a circular motion.

As a glacier gets heavier, it begins to move downhill. Fed from the top, the glacier moves out of the hollow in a semi-circular motion, as illustrated above. This is called rotational slip.

It makes the hollow deeper by eroding the rock at the bottom of the hollow. Where the ice leaves this "bowl", it leaves behind rock fragments which eventually form a lip.